unionfs stack trace

note that the stack details above are in dmesg.... My userapp just crashes with segv.

This appears to be the same as #209547 but this is for another app not for openoffice.

Chris, could you share you app with me, then I could use it to debug this issue.

I cannot publically share the actual app which is quite large but I was able to create a simple reproducer which should be even better... :-)

When the file is on unionfs this basically hangs during the ftruncate call and dmesg reports the error. The process becomes pretty unkillable.

#include <stdio.h>
#include <stdlib.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>

#define FNAME "/tmp/myfile"

main() {
  int f,s;
  f=open(FNAME,O_RDWR|O_CREAT|O_EXCL,0600);
  fprintf(stderr,"open f=%d\n",f);
  s=unlink(FNAME);
  fprintf(stderr,"unlink status=%d\n",s);
  s=write(f,"hi",3);
  fprintf(stderr,"write status=%d\n",s);
  s=ftruncate(f,0);
  fprintf(stderr,"truncate status=%d\n",s);
}

Jay, any progress on tracing this bug?

No, I could only test the latest unionfs (upstream). I will continue working on this after I finish the "profiling of USB suspend/resume"

Thanks
+Jay

-----Original Message-----
From: <email address hidden> [mailto:<email address hidden>] On Behalf Of alek du
Sent: Sunday, April 13, 2008 7:31 PM
To: Chetty, Jay
Subject: [Bug 210581] Re: unionfs stack trace

Jay, any progress on tracing this bug?

** Changed in: moblin-kernel
   Importance: Undecided => Low

--
unionfs stack trace
https://bugs.launchpad.net/bugs/210581
You received this bug notification because you are a bug assignee.

Jay, since you are busy with other tasks, I tried to trace the case and root caused the bug:

in fs/unionfs/inode.c 1009 line

lower_inode = unionfs_lower_inode(inode);

here lower_inode has the possibility to be NULL !!!

Add lines:
if (!lower_inode) {
                err = -ENOENT;
                goto out;
        }

to fix that. Will do more test and commit to Moblin kernel.

Code committed to Moblin kernel but currently I have no way to release it.

 diff --git a/fs/unionfs/inode.c b/fs/unionfs/inode.c
 new file mode 100644
-index 0000000..6dee4ac
+index 0000000..ea10d77
 --- /dev/null
 +++ b/fs/unionfs/inode.c
-@@ -0,0 +1,1097 @@
+@@ -0,0 +1,1101 @@
 +/*
 + * Copyright (c) 2003-2007 Erez Zadok
 + * Copyright (c) 2003-2006 Charles P. Wright
@@ -5727,6 +5727,10 @@ index 0000000..6dee4ac
 +
 + lower_inode = unionfs_lower_inode(inode);
 +
++ if (!lower_inode || !lower_dentry) {
++ err = -ENOENT;
++ goto out;
++ }
 + /*
 + * If shrinking, first truncate upper level to cancel writing dirty
 + * pages beyond the new eof; and also if its' maxbytes is more

Excellent! Hopefully it will come thru whenever the next Moblin kernel update happens.

Thanks,
Chris

I need build server to build "master" branch of Moblin kernel -- otherwise I have no change to close this bug.

There is no way to build moblin kernel, will this patch be applied to UME kernel? and you will submit it as kernel PPA?

I already sent the patch to Jay and Amit (Ubuntu kernel team), do not know if they apply my patch yet. Include Jay in the loop.

Thanks
Alek
-----Original Message-----
From: <email address hidden> [mailto:<email address hidden>] On Behalf Of May Xie
Sent: 2008年5月19日 22:57
To: Du, Alek
Subject: [Bug 210581] Re: unionfs stack trace

There is no way to build moblin kernel, will this patch be applied to
UME kernel? and you will submit it as kernel PPA?

** Changed in: moblin-kernel
       Target: m11 => None

--
unionfs stack trace
https://bugs.launchpad.net/bugs/210581
You received this bug notification because you are a bug assignee.